fix(core,player,studio): bound trimmed audio playback to the clip window (#1430)

* fix(player): bound the parent audio proxy to its clip window

When iframe autoplay is blocked, audible playback is promoted to a parent-frame
audio proxy. The proxy read the clip's data-start/data-duration once at adopt
time and mirrorTime() only skipped (never paused) the element outside that
window — so a trimmed/moved music clip kept playing the full source past its
on-timeline end, even though the iframe element was correctly paused.

Fix: the proxy keeps a reference to its source iframe element and re-reads
data-start/data-duration each mirror tick (live trims/moves apply), pauses the
proxy when the playhead leaves [start, start+duration), and resumes it when the
playhead re-enters during parent-owned playback.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Co-authored-by: Miguel Ángel <miguel07alm@protonmail.com>

* fix(core,studio): bound trimmed audio playback to the clip window

Trimmed audio played to the source file's natural end instead of
stopping at the clip edge, on every audio path:

- WebAudio (the audible path in Studio): schedulePlayback now passes
  the clip's data-duration as the third start() arg, so the decoded
  buffer stops at the trimmed edge instead of running to the file end.
- Runtime element gating: the duration resolver caps each clip by its
  own data-duration (min of source length, host window, authored
  duration), so a trimmed <audio>/<video> element pauses at its edge.

Studio trim UX:

- Resize live-patches the media-start/playback-start offset, so a
  start-edge drag trims into the source instead of only repositioning
  the clip.
- AudioWaveform windows the rendered peaks to the trimmed slice so the
  waveform tracks the clip edges.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Co-authored-by: Miguel Ángel <miguel07alm@protonmail.com>

* fix(player,core): gate proxy playback to the live clip window

Review follow-ups on the parent-audio-proxy / WebAudio bound:
- seekAll now re-reads live source bounds (_refreshEntryBounds) before
  gating, so a paused scrub right after a trim/move uses the current clip
  window instead of the adopt-time one.
- playAll and clip adoption only start a proxy when the playhead is inside
  the clip's window (_playEntryIfActive), so bulk starts / promotion no
  longer blip audio for clips outside their window until the next tick.
- The WebAudio buffer is now bounded by the host-composition window too
  (matching resolveDurationSeconds), so a sub-composition-nested clip stops
  at the same edge on the WebAudio and HTMLMedia paths.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Co-authored-by: Miguel Ángel <miguel07alm@protonmail.com>

* fix(core,player): reschedule bounded WebAudio on rate change; guard NaN bounds

A bounded WebAudio source's wall-clock length is baked into start()'s duration
arg (in buffer-sample seconds) at its scheduling rate. Mutating playbackRate in
place on a later rate change does not rescale that bound, so a trimmed clip ends
early (fast) or late (slow). setRate now reports whether the rate changed and
exposes hasBoundedActiveSources(); the runtime stopAll()+reschedules active
clips at the new rate when any bounded source is live. The per-clip schedule
loop is extracted to a shared closure so play() and the rate path agree.

Also guard _refreshEntryBounds against a non-numeric duration attribute parsing
to NaN, which would make every window check false and let the proxy play past
its clip end.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Co-authored-by: Miguel Ángel <miguel07alm@protonmail.com>

---------

Co-authored-by: Miguel Ángel <miguel07alm@protonmail.com>

packages/studio/src/player/components/AudioWaveform.tsx

@@ -5,6 +5,17 @@ interface AudioWaveformProps {
   waveformUrl?: string;
   label: string;
   labelColor: string;
+  /**
+   * Fraction (0–1) of the source the clip starts at, after the media-start
+   * trim. Defaults to 0 (no front trim).
+   */
+  trimStartFraction?: number;
+  /**
+   * Fraction (0–1) of the source the clip ends at. Defaults to 1 (no tail
+   * trim). Together these window the rendered peaks to the trimmed slice so the
+   * waveform tracks the clip edges instead of squeezing the whole file in.
+   */
+  trimEndFraction?: number;
 }
 
 const BAR_W = 2;
@@ -62,6 +73,8 @@ export const AudioWaveform = memo(function AudioWaveform({
   waveformUrl,
   label,
   labelColor,
+  trimStartFraction,
+  trimEndFraction,
 }: AudioWaveformProps) {
   const containerRef = useRef<HTMLDivElement | null>(null);
   const barsRef = useRef<HTMLDivElement | null>(null);
@@ -116,20 +129,28 @@ export const AudioWaveform = memo(function AudioWaveform({
     const barsEl = barsRef.current;
     if (!container || !barsEl || !peaks) return;
 
+    // Window the peaks to the trimmed slice [start, end) of the source so the
+    // bars track the clip edges. Clamp to a valid, non-empty range.
+    const winStart = Math.max(0, Math.min(1, trimStartFraction ?? 0));
+    const winEnd = Math.max(winStart, Math.min(1, trimEndFraction ?? 1));
+    const lo = Math.floor(winStart * peaks.length);
+    const hi = Math.max(lo + 1, Math.ceil(winEnd * peaks.length));
+    const span = hi - lo;
+
     const w = container.clientWidth || 400;
-    const barCount = Math.min(Math.floor(w / STEP), peaks.length);
+    const barCount = Math.min(Math.floor(w / STEP), span);
 
     let html = "";
     for (let i = 0; i < barCount; i++) {
-      // Map bar index to peak index (resample)
-      const peakIdx = Math.floor((i / barCount) * peaks.length);
+      // Map bar index to peak index within the windowed range (resample)
+      const peakIdx = lo + Math.floor((i / barCount) * span);
       const amp = peaks[peakIdx] ?? 0;
       const pct = Math.max(3, Math.round(amp * 100));
       const opacity = (0.45 + amp * 0.4).toFixed(2);
       html += `<div style="position:absolute;bottom:0;left:${i * STEP}px;width:${BAR_W}px;height:${pct}%;background:rgba(75,163,210,${opacity})"></div>`;
     }
     barsEl.innerHTML = html;
-  }, [peaks]);
+  }, [peaks, trimStartFraction, trimEndFraction]);
 
   // Observe container size and redraw
   const setContainerRef = useCallback(